The present invention relates generally to metal working fluid or machine coolant management systems, and more particularly, to a system which includes components that are capable of being placed in the working fluid as a unit for purposes of selective withdrawal of the fluid and separation of its contaminants. The unit is useful primarily with so-called machining centers, but also with parts washers and other forms of apparatus which use water as their process fluids.
The term "coolant" is intended to be an all-inclusive term, which includes water, any number of emulsifying agents, cutting oils and lubricants of various kinds, additives, and impurities created by cutting, drilling or other machining operations, including grinding or abrasive metal reduction. The term also includes fluids not strictly used for cooling but which are nonetheless subject to oil/water separation, such as those used in aqueous-based parts washers. For purposes of illustration, however, the description herein is primarily directed to machining centers.
In the preferred form, a floating skimmer and feed pump are placed in the user's machine sump and are able to transport oil and contaminant-laden coolant to the treatment elements. The remainder of the elements making up the system are preferably contained in a unified housing to simplify their installation or placement and, very importantly, to ease the burden of periodically servicing the machine. The servicing, of course, is carried out by a contractor who specializes in these and similar products.
In the preferred form, the unified components contained in a housing are removable and, replaceable, if need be, as a unit, and the components which are used in the machine coolant tank may be removed therefrom without in any way disturbing the integrity of the machining operation.
Preferably, the system contains both a floating contaminant removal device, termed a "skimmer", and a submersible pump, each with its own impurity or contaminant removal system. The coolant liquid itself is continuously recirculated, preferably by means of a centrifugal pump and fed through a low-pressure-drop filter. Once the process fluid has passed through this filter, the liquid is returned in a substantially particulate-free condition to the coolant bath. At the same time, the oils and other lighter-than-water contaminants are picked up from the top surface of the coolant by a floating skimmer of a novel design, and directed via suitable tubing through an oil trap of a novel design, through a filter, and finally, through a positive displacement pump before being returned in a substantially oil-free condition to the coolant bath. The oil trap removes tramp oil, floating solids, and other non-emulsified, lighter-than-coolant impurities.
The system is designed to clean and maintain a coolant system which is primarily water, but also contains, in most cases in emulsion form, a lubricant for the machine, and various surface active agents which maintain the oil-water emulsion and prevent corrosion. There may be other components whose identity will vary somewhat with the application and the details of whose composition is not particularly relevant to the present invention.
An advantage of the present invention is that it gives an outside contractor or supplier the ability periodically to service the separate apparatus without disturbing the principal machine, or compromising its operation. Thus, service may be performed by removing the oil from the trap or separator and removing the used filter element. This is accomplished merely by disconnecting the electrical power supply to the pump and disconnecting the fluid conduits leading to the coolant management system. Then, the housing is serviced by replacing the filter element and collecting the separated oil from the oil trap. In this way, the customer's principal machine need undergo no significant down time, or no down time at all. Most or all of the maintenance can be performed without stopping the machine.
The skimmer and the hose connecting it to the remainder of the apparatus may be simply serviced or replaced, because the skimmer has no moving parts and only one adjustable part, that is one which may be adjusted simply by turning the insert to adjust the skim gap. Likewise, the centrifugal, submersible feed pump may be removed and replaced, if necessary, since this unit itself contains only a strainer and includes minimal, self-contained moving parts. It is preferably a pump that may be adjusted to a desired depth, but is otherwise modular and removable. The depths to which the unit may be submerged are varied for example simply by changing the position of the hanger bracket.
In a preferred form, a single, preferably plastic outer container contains the oil trap, the small positive displacement pump filter, and the positive displacement pump itself, as well as the so-called "cross flow" filter and its connecting lines.
The construction of the oil trap is such that a generally non-emulsified oil-water mixture enters the trap manifold and the liquid phase is directed downwardly well past the middle of the trap. As the oil coalesces, it floats to the top and forms several layers, an air layer, an oil layer, an emulsified layer, a lowermost water layer and of course a sludge layer resting on the bottom. Accordingly, the water phase lies adjacent the bottom of the oil trap housing. The plates on the return tube prevent turbulence and thus help with separation of water and allow the water to pass up inside the return tube. The return tube has a connection to the positive displacement pump, and also is in communication with the air in the air-tight manifold. The oil accumulates below the manifold portion of the oil trap. The water passes from near the bottom to the return tube and hence is substantially oil-free. A strainer and a screen comprise the filter protecting the suction pump from impurities on this portion of the apparatus.
The positive displacement pump is preferably a bellows- or diaphragm-type pump which is operated by a cam, and functions at a relatively low flow rate. A bellows- or diaphragm-type pump is selected because of its self-priming capability. Preferably, the rate of the flow of the oil pump is selected so as to allow an appropriate residence time for oil and water separation within the oil trap. Additionally, a positive displacement pump provides low shear forces. The centrifugal pump is a submersible type which operates with a relatively small pressure head and supplies coolant, suspended solids, including particles and contaminants, to the filter.
The makeup of this type of filter is best shown in U.S. Pat. No. 5,478,465, wherein two sleeves, each having tortuous flow paths, are interconnected to an outside manifold outlet which allows the coolant to enter the return line after the coolant has been filtered. All of the coolant emerges from the filters, and this arrangement of the filter permits the filter not to be "blinded" or to lose its capacity to filter although part or even most of it may be eventually clogged during operation.
A bypass opening on the filter may permit flow to continue in the event of clogging, thereby protecting the pump from becoming partially or fully clogged during operation.
In view of the failure of the prior art to provide a simple, integrated cost-effective, low pressure, very serviceable and low maintenance integrated system for liquids, including managing coolant used in cutting, drilling, grinding or other machining operations, it is an object of the present invention to provide such an integrated system.
It is another object of the invention to provide a coolant management system, which, except for the pickup and discharge elements, lies entirely outside the principal apparatus, and hence is independent of such apparatus.
Yet another object of the invention is to provide a coolant treating system which will both pick up coolant and suspended solid components and pass such components through a suitable filter, as well as a floating pickup unit including a novel skimmer for processing lighter than water components, including oil and the like.
Still another object of the invention is to provide an apparatus which includes units for purifying a water-oil emulsion emanating from both immersed and surface sources.
A further object of the invention is to provide an apparatus using appropriate, different style pumps, preferably one centrifugal and one positive displacement pump, for scavenging different contaminants in a liquid from the same coolant bath.
A still further object of the invention is to provide a one-piece container for two elements, preferably cylindrical elements, respectively containing an oil trap and a suspended particles filter.
An additional object of the invention is to provide pumps in an apparatus, which are operable by ordinary, plug-in low voltage shop current available in any locations.
A still further object of the invention is to provide an apparatus wherein the periodic servicing may be carried out in a matter of minutes, which is due to the arrangement of components.
Another object of the invention is to provide a filter and oil trap separators which may be serviced and/or removed and replaced by a service organization without materially disturbing the operation of the customer's principal system/machine.
Another object of the invention is to provide an oil trap with a three-way air bypass, including a bleed hole for return air.
A still further object of the invention is to provide a skimmer device having a readily and easily adjustable skim gap, so that the skimmer will be less sensitive to temperature changes in the bath, and also to accommodate slight changes in fluid density.
An additional object of the invention is to provide a return tube having two concentric plates on it to help phase separation and prevent re-emulsification, thereby permitting substantially only water to enter the return tube.